Generally, in MIMO communication system, a transmitting antenna switching system is used as a method for securing spatial diversity. This transmitting antenna switching system can be mainly categorized into an open-loop antenna switching system and a closed-loop antenna switching system in accordance with whether feedback information indicating a channel status per each antaean is used or not.
FIG. 1 is a block diagram for a configuration of an open-loop antenna switching system. open-loop antenna switching system.
Referring to FIG. 1, in an open-loop antenna switching system, a transmitting side randomly selects an antenna for transmitting data and then transmits data and reference signals. The open-loop antenna switching system employs a structure that uses the small number of RF chains in switching transmitting antennas to transmit data in an overall system for transmission and reception using a plurality of transmitting and receiving antennas.
In particular, a resource allocation module 101 plays a role in deciding and sending a frequency or time and space (antenna) for transmitting data and reference signals. And, a switching module 102 enables the data and reference signals received from the resource allocation module 101 to be transmitted via a randomly selected antenna for each transmission. In this case, a plurality of transmitting antennas are available and the number of the RF chains can range from one to the maximum number of the transmitting antennas.
The above-described antenna switching system is provided to obtain spatial diversity in transmitting data using transmitting antennas alternately in an environment difficult to have transmitting RF chains enough (e.g., in an uplink system, a user equipment (UE) is difficult to have a multitude of RF chains).
FIG. 2 is a diagram for details in operating a resource allocation module and a switching module in the open-loop antenna switching system shown in FIG. 1.
FIG. 2 depicts a method of transmitting data and reference signals (carried between data signals) as packets in a system having two transmitting antennas and a single RF chain, in which the packet may have a single subcarrier structure or a structure that utilizes a plurality of subcarriers in such a system as OFDM system. An arrow shown in FIG. 2 indicates that an antenna is switched.